Photoreceptors for electrophotography include those in which a photoconductive layer has a single layer structure and those in which a photoconductive layer has a laminated structure. In recent years, many proposals have been directed particularly to organic photoreceptors whose photoconductive layer contains an organic photoconductive material dispersed in a binder resin and has the layer structure of separate function composed of a charge transport layer and a charge generating layer, as disclosed, e.g., in Japanese patent application (OPI) Ser. Nos. 52756/81 and 73743/82 (the term "OPI" as used herein means an "unexamined published Japanese patent application"). Binder resins proposed for use in the charge transport layer include polycarbonate resins, polyester resins, polymethyl methacrylate resins, bisphenol Z polycarbonate resins as described in Japanese patent application (OPI) Ser. No. 71057/84, and the like.
However, application of electrophotographic photoreceptors containing the above-described organic photoconductive materials and binder resins to commonly employed electrophotographic systems, such as a Carlson process, has been accompanied by various problems. For example, a charge transport material forms a charge transfer complex with some specific resins used as binder resin for a charge generating material. As a result, the photoreceptor entirely fails to be charged, or the charge transport material undergoes deterioration due to changes with time to cause so-called photo-fatigue.
Further, in photoreceptors in which a charge transport layer containing a charge transport material and a binder resin is provided as an outermost layer (top layer), problems such as adhesion of toners onto the charge transport layer, wear or scratches of the charge transport layer due to contact with a developer or transfer paper, and the like occur. The aforesaid polycarbonate resins, polyester resins, polymethyl methacrylate resins, or the like are unsatisfactory to solve these problems, exhibiting insufficient electrophotographic characteristics when used as binder resin in the charge transport layer. On the other hand, the bisphenol Z polycarbonate resins have a disadvantage when used as binder resin in combination with some specific charge transfer materials in that the resulting photoreceptors are not charged at all.